1. Field of the Invention
The present invention is related to a driving circuit and driving method thereof, and particularly to a driving circuit and driving method thereof that can enhance energy conversion efficiency through staged load driving.
2. Description of the Prior Art
Please refer to FIG. 1A. FIG. 1A is a diagram illustrating a driving circuit 100 for driving light emitting diodes according to the prior art. As shown in FIG. 1A, the driving circuit 100 includes a rectifier 102 and a current supply unit 104. The rectifier 102 is used for receiving an alternating current voltage AC, and generating a first voltage V1 according to the alternating current voltage AC. The first voltage V1 is a direct current voltage and varies with time periodically. The first voltage V1 is used for driving a series of light emitting diodes 106, and the series of light emitting diodes 106 includes at least one light emitting diode. In FIG. 1A, input power of the driving circuit 100 is a sum of power consumption of the series of light emitting diodes 106 and power consumption of the current supply unit 104. Please refer to FIG. 1B. FIG. 1B is a diagram illustrating a relationship between the power consumption of the series of light emitting diodes 106 in FIG. 1A and the first voltage V1. As shown in FIG. 1B, the more light emitting diodes of the series of light emitting diodes 106 (that is, the larger a voltage drop V106 of the series of light emitting diodes 106), the larger the power consumption P106 of the series of light emitting diodes 106 (a driving current for driving the series of light emitting diodes 106 times the voltage drop V106), resulting in the smaller the power consumption of the current supply unit 104. However, a turned-on interval T of the series of light emitting diodes 106 is shorter, so luminance of the series of light emitting diodes 106 is insufficient.
Please refer to FIG. 2A and FIG. 2B. FIG. 2A is a diagram illustrating a driving circuit 200 for driving light emitting diodes through staged driving according to the prior art, and FIG. 2B is a diagram illustrating a relationship between power consumption of light emitting diodes in FIG. 2A and the first voltage V1. As shown in FIG. 2A, the driving circuit 200 includes a rectifier 202 and a current supply unit 204. As shown in FIG. 2B, as the first voltage V1 is gradually increased, light emitting diodes 2062, 2064, and 2066 of a series of light emitting diodes 206 are turned on in turn. That is to say, when the first voltage V1 is equal to a voltage V2062, the light emitting diode 2062 is turned on (the light emitting diodes 2064 and 2066 are turned off), and a driving current for driving the light emitting diode 2062 flows to the current supply unit 204 through a node S1. Similarly, when the first voltage V1 is equal to a voltage V2064, the light emitting diodes 2062, 2064 are turned on (the light emitting diode 2066 is turned off) and a driving current for driving the light emitting diodes 2062, 2064 flows to the current supply unit 204 through anode S2. When the first voltage V1 is equal to a voltage V2066, the light emitting diodes 2062, 2064, and 2066 are turned on and a driving current for driving the light emitting diodes 2062, 2064, and 2066 flows to the current supply unit 204 through a node S3. Therefore, as shown in FIG. 2B, the driving circuit 200 can increase power consumption of the series of light emitting diodes 206. That is to say, the power consumption of the series of light emitting diodes 206 is equal to a sum of power consumption P2062 of the light emitting diode 2062, power consumption P2064 of the light emitting diode 2064, and power consumption P2066 of the light emitting diode 2066. Thus, the driving circuit 200 can drive more light emitting diodes connected in series, enhance energy conversion efficiency, and not reduce luminance of the series of light emitting diodes 206. However, a disadvantage of the driving circuit 200 is that luminance of the light emitting diode 2066 is always lower than luminance of the light emitting diodes 2062 and 2064.